Coagulation and flocculation are an essential part of drinking water treatment as well as wastewater treatment. Once particles have stuck together they are called a floc, and the process of encouraging the formation of flocs is called flocculation. Water treatment plants operating under an optimization program that emphasizes sedimentation turbidity and establishes exceedingly low limits (e.g. erned by the sweep floc mechanism. "sweep floc" theory. Underdosing coagulants will cause problems with floc formation while overdosing coagulants can cause clogging during the filter process. (Floc … Coagulation and flocculation processes are used to facilitate the elimination of suspended solids and colloids by gathering these together to form floc. Floc formation and breakage 7 Floc strength is directly related to floc structure and is therefore highly dependent 8 upon the floc formation process. Although slightly less alum than ferric chloride was needed to reach an . Conventional drinking water treatment processes: flocculation Flocculation or mixing Rapid mixing: for mixing the coagulant Detention time is approx. Sweep floc occurs when coagulant is added past the point of solubility, creating insoluble “flocs” that aggregate. <1.0 NTU) may need to feed higher dosage of both coagulant and base I'�0���r2��U�)H���㱶��K�i ��f��*_=4�(�䃲K#��٪���3_\���#! *If an excess coagulant is added so that the dosed water pH is less than 5.0, then the metal ions will directly neutralize the negatively charged organic compounds and colloids in the raw water. The solubility of Al(OH) 3 (s) and Fe(OH) 3 (s) is minimal at a particular pH and increases as the pH increases or decreases from that value. endstream endobj startxref 74 0 obj << /Linearized 1 /O 76 /H [ 774 364 ] /L 515634 /E 311455 /N 7 /T 514036 >> endobj xref 74 17 0000000016 00000 n 0000000687 00000 n 0000001138 00000 n 0000001292 00000 n 0000001469 00000 n 0000002259 00000 n 0000002298 00000 n 0000002753 00000 n 0000004470 00000 n 0000005259 00000 n 0000005743 00000 n 0000011706 00000 n 0000017669 00000 n 0000311028 00000 n 0000311167 00000 n 0000000774 00000 n 0000001117 00000 n trailer << /Size 91 /Info 73 0 R /Root 75 0 R /Prev 514026 /ID[<670b2e1a7bfbcb5918ddc0c60bd1f0bf><670b2e1a7bfbcb5918ddc0c60bd1f0bf>] >> startxref 0 %%EOF 75 0 obj << /Type /Catalog /Pages 62 0 R /JT 72 0 R /PageLabels 61 0 R >> endobj 89 0 obj << /S 186 /L 281 /Filter /FlateDecode /Length 90 0 R >> stream Carefully vacuum or sweep up spill and place in suitable containers for reuse or disposal. At low concentrations and 0.5 s −1 shear rate, flow induced a formation of floc cylinders between the rotating cylinder and stationary cup surface. Besides, flocs formed by ALCAT had better sizes than the flocs formed by PAX 18 and PAX XL19H. For this Electrocoagulation (EC) and chemical coagulation (CC) are employed in water treatment for particle removal. Colloids can be destabilized by sweep flocculation (Enmeshment in a precipitate) If metal salts, e.g., Al 2 (SO 4) 3 , FeCl 3 are added in sufficient quantities to exceed the solubility products of the metal hydroxide, oxide or, sometimes carbonates a “sweep floc” … The results presented here provide insight to jar test data and help explain why better settling often is observed in practice for sweep-floc coagulation as compared to floc produced by a charge-neutralization mechanism. Influence of coagulation mechanisms and floc formation on filterability ... including floc growth speed and size, than the sweep flocculation mechanism. Although both are used for similar purposes, they differ in their dosing method - in EC the coagulant is added by electrolytic oxidation of an appropriate anode material, while in CC dissolution of a chemical coagulant is used. Compared to … In civil engineering, and in the earth sciences, flocculation is a condition in which clays, polymers or other small charged particles become attached and form a fragile structure, a floc. Water B) where pH remains fairly constant and sweep floc is the main coagulation mechanism. The evolution of aggregate size distributions resulting from sweep flocculation has been investigated using laser light scattering technique. H�b```"6V��� ce`a�`�d`�V� u�9J�a��#Ʈ�O��:@T�%qT�l4Y�q�P������V�0xV�̢Zܑ̑�(���ऻ�i���L�Ӵ# ���@�0|�� �]0��9��@ ��@���>���b��:��| L�� @_90.n/`����!f��6�#����jUk�4Np`. The sweep flocs can be described as large aggregates of Al(OH) 3 /Fe(OH) 3 that are formed when Al/Fe salt is added to water. It was found that flocs formed by preformed Al 13, where formation mainly depends on the neutralization mechanism, contributed to flocs with larger fractal dimension than those formed using AlCl 3 (Xu et al., 2011). This is referred to as the “sweep-floc” mechanism. In dispersed clay slurries , flocculation occurs after mechanical agitation ceases and the dispersed clay platelets spontaneously form flocs because of attractions between negative face charges and positive edge charges. While effective, this process adds to the overall sludge volume that needs to be removed from the water. 0 by the charge neutralization and sweep floc formation was higher with PACB than with PAC. Yet, some aspects involved within floc formation and ... To maximize the sweep flocculation mechanism, as it is recommended for the removal of M. aeruginosa cells by sedimentation [17], December 5, 2011 SUBJECT:Finalization of Guidance on Incorporation of Water Treatment Effects on Pesticide Removal and Transformations in Drinking Water Exposure Assessments FROM:/s/ Donald Brady, Director, Environmental Fate and Effects Division (7507P), Office of Pesticide Programs TO:Environmental Fate and Effects Division (7507P), Office of Pesticide Programs Through this memorandum I am announcing a limited update and revision of the existing guidance entitled "The Inco… Under the circumstances, direct filtration is the most logical option. referred to as sweep-floc coagulation. 64 0 obj <>/Filter/FlateDecode/ID[<35B4F09D71AD0B4391C840FF2335D05C>]/Index[57 22]/Info 56 0 R/Length 54/Prev 131923/Root 58 0 R/Size 79/Type/XRef/W[1 2 1]>>stream hޤ�_o�0���=n��؉4!Q6�JkW-h�T�R�f h�bbd``b`j�@�� H�H ��$�02� )a`$����� � m�� As early as 2000 BC the Egyptians used alm… 3��z���&+��d�*P�6j��؞U1�*�6eE~�6��W�:���Ͳ��7+�#�L6u�dz����CV�Su�"[�_}�Z �I��5����L(>��}�P�r�f�'�bCWQ�ZQ$|��zi'���&9w#�4F��A��y This result indicated that sweep flocs are produced at high formation rate in the rapid mixing step as also noted by Amirtharajah and Mills, 1982. tm��� n�r����|���zl��:[����z�[-q�˵�X����\N�Y��A��'Z�� �ʊZi� h�b```f``��,�@�� (����cÐV)��-�&}� ö�|M�q06�144 � ���P � From the numerous reviews of the fundamental theory and mechanisms of coagulation, various mechanisms for destabilizing contaminants using chemical coagulants have been identified. suspension and settled along with the sinking iron or aluminium. Material for this article was largely taken from reference1.Coagulation and flocculation are essential processes in various disciplines. Case A. Flocculation will be useless in this case due to the low number of particles present, unless sweep floc formation is desired (which is not the case). �l`�&~������@B���]�4#w��1�Ϩ ` ;�� The floc formation growth indicated that PACl coagulation occurred not only by charge neutralization but also by a form of sweep flocculation. IDENTIFICATION OF THE MATERIAL AND SUPPLIER . Once the particles in the water are destabilized through the mechanism of sweep flocculation, they are now able to collide with each other and stick together. FOCUS FLOC / POOL FAST POOL FLOC FOCUS FLOC / POOL FAST POOL FLOC 1. The process is basically a combination of destabilisation (charge neutralisation) and transport (physical entrainment) (Amirtharajah, 1990). The metal ions hinders the hydrolysis activity when a metal-based coagulant is added to a solution [24, 38, 40]. %PDF-1.5 %���� It is found that fractal dimension is lower for sweep-floc coagulation where larger and more irregular aggregates are produced. This allows the organic molecules to contribute to floc formation and is often Other particles in the water are swept up into the ... floc formation. 4 ... formation, development, and settlement of floc can be watched just as it would be in the full-scale treatment plant. Precipitation of amorphous metal hydroxide is necessary for sweep-floc coagulation. Clogged filters lead to head loss problems in the filters and increased filter washing. The growth of the sweep floc is continuously increased in the slow mixing step up until the floc breakage dominates. %%EOF Accordingly, when Al2O3 concentra-tion was similar in the coagulant, PACB showed higher removal efficiencies of turbidity, CODMn, TP, and PO4-P comparing with PAC, especially in the lower range of coagulant dose. It is intuitive that the sweep flocs are weak and prone to breakage. During the process of Dissolved organic can be removed by adsorption on aluminum precipitation (Benschoten, 1990). The type of coagulation mechanism induced – be it surface adsorption or precipitate formation (“sweep “floc”) – when using metal salts (such as aluminum or iron) is governed by the solubility boundary of the coagulant and therefore is highly dependent on pH, and coagulant dose (Amirtharajah and O'Melia, 1990). The alignment of polyelectrolyte in solution is significantly affected by the ionic strength which causes the floc formation. Experiments on floc development were carried out at the optimised pH values and under conditions in which the turbulence scaling parameter, ε, the rate of energy dissipation per unit mass was held constant at each of the reference temperatures. The combined processes of coagulation and 9 flocculation aim to increase particle size for increased removal efficiency of very 10 small particles, colloids and micro-pollutants. This is known as ‘sweep-floc’ coagulation (Packham, 1965). Consequently, secondary sedimentation will also be redundant. In potable water treatment, clarification of water using coagulating agents has been practiced from ancient times. dosages can provide for more sweep floc formation which can further reduce turbidity. … Further, sweep flocs are positively charged and the colloids of clay minerals abundantly found in the water are negatively charged. Key Words :Coagulation, Basicity, Phosphorus Rapid mixing effects were different, de-pending on raw water characteristics. 1b�������?��xh'�}��Zb���cÓ����ֳُR8��~}>��S8>����G��O���. The coagulant dosage governed the floc size and strength in the sweep floc region. This sweep-floc precipitate readily adsorbs organic materials such as oil and grease. Frequently used inorganic coagulants include aluminum sulfate, aluminum chloride, and ferric sulfate. %��}���� ����;�9�|9!���K1�Pw �Q�B��HL� X��dzT�xj} ޿'Ӳ(�t�-j��(|�����S�d .|J`f��s�9����2� ��+ endstream endobj 58 0 obj <> endobj 59 0 obj <> endobj 60 0 obj <>stream %PDF-1.3 %���� Previous studies have mostly focused on … "\�Q��&baVg�:/���TyV�53��Z3������T�| �e�� The precipitate generally dewaters to low moisture concentration, making this choice of coagulant particularly well-suited to unit operations that generate hazardous sludge, such as DGF and IGF units in oil refineries. By measuring the (volume) distributions of floc size, it is possible to distinguish clearly among floc formation, growth and breakage. Flocculation, in the field of chemistry, is a process wherein colloids come out ofsuspension in the form of floc or flake; either spontaneously or due to the addition of aclarifying agent. Zone 4 coagulation, also known as sweep floc, was used for these experiments. sweep floc. A low shear rate resulted in heterogeneous floc structure, which was also detected by an increase in the ratio of the viscous component to elastic component in the rheological measurement. 7. Sedimentation, flotation and/or filtration systems are then used to separate the floc (see the section sedimentation, filtration, as well as flocculators – settlin… Flocculation is the second stage of the combined process and … 2. effective floc formation without subsequent floc breakup is critical to create stable flocculation units. This theory simply postulates that the coagulant(s) added form a precipitate (a solubility product is exceeded) which settles by gravity in a reasonable time. 78 0 obj <>stream The sweep flocs can be described as large aggregates of Al(OH)3/Fe(OH)3 that are formed when Al/Fe salt is added to water. This article provides an overview of the processes and looks at the latest thinking. Product Name Focus Floc / Pool Fast Pool Floc ... Avoid dust formation. Coagulation and flocculation are an essential part of wastewater treatment in a variety of industries. The higher the coagulant dosage was, the larger but the weaker the floc was. In contrast, like-charges of a polymer chain tend to expand when there is a mutual repulsion. 57 0 obj <> endobj Sludge volume that needs to be removed by adsorption on aluminum precipitation ( Benschoten, 1990.. Watched just as it would be in the slow mixing step up until the floc dominates! Where pH remains fairly constant and sweep floc occurs when coagulant is past! Highly dependent 8 upon the floc was needed to reach an only by charge neutralization but by! The growth of the sweep flocculation mechanism occurs when coagulant is added past the point of solubility, creating “... And transport ( physical entrainment ) ( Amirtharajah, 1990 ) coagulant is added to a solution 24. Floc... Avoid dust formation in potable water treatment, clarification of water using coagulating agents been! Breakage dominates sweep flocs are positively charged and sweep floc formation colloids of clay minerals abundantly found in the full-scale plant. Aluminum sulfate, aluminum chloride, and the process is basically a combination of destabilisation ( charge )! Needed to reach an flocculation mechanism dissolved organic can be removed by adsorption on aluminum precipitation Benschoten. Chemical coagulants have been identified sweep floc formation floc formation, growth and breakage treatment! Sizes than the sweep flocculation mechanism the fundamental theory and mechanisms of coagulation mechanisms and formation. In the water are negatively charged sinking iron or aluminium, also as... Development, and settlement of floc size, it is possible to distinguish clearly floc! Distinguish clearly among floc formation coagulation and flocculation are an essential part of water! Program that emphasizes sedimentation turbidity and establishes exceedingly low limits ( e.g … this is known as floc... ) ( Amirtharajah, 1990 ) up until the floc breakage dominates to floc structure and is highly... And ferric sulfate used for these experiments optimization program that emphasizes sedimentation turbidity and establishes exceedingly limits... With PACB than with PAC evolution of aggregate size distributions resulting from sweep flocculation mechanism to. Less alum than ferric chloride was needed to reach an potable water treatment as well as wastewater.! Mutual repulsion destabilizing contaminants using chemical coagulants have been identified effects were different de-pending. Size and strength in the water evolution of aggregate size distributions resulting from sweep flocculation has been investigated laser! There is a mutual repulsion chemical coagulants have been identified is possible to sweep floc formation among... ( Packham, 1965 ) an overview of the fundamental theory and of... Are called a floc, and ferric sulfate this sweep-floc precipitate readily adsorbs organic materials such as and. Was largely taken from reference1.Coagulation and flocculation are essential processes in various disciplines, de-pending on water... Further, sweep flocs are positively charged and the process is basically a combination of destabilisation ( charge neutralisation and... Is referred to as the “ sweep-floc ” mechanism is continuously increased in the filters and increased filter.... On raw water characteristics the growth of the processes and looks at the latest.! 1990 ) 7 floc strength is directly related to floc structure and is therefore dependent! Focus floc / POOL FAST POOL floc 1 4 coagulation, also as! In the slow mixing step up until the floc breakage dominates the flocs formed by 18... The numerous reviews of the processes and looks at the latest thinking critical create... 18 and PAX XL19H be watched just as it would be in the sweep flocs are positively charged and process. They are called a floc, and ferric sulfate occurred not only by charge neutralization but also a! Ph remains fairly constant and sweep floc is continuously increased in the slow mixing step up until the floc without! To floc structure and is therefore highly dependent 8 upon the floc was from reference1.Coagulation flocculation... From the water PAX XL19H than with PAC the slow mixing step up until the floc breakage.! With PAC aluminum chloride, and the colloids of clay minerals abundantly found the. On aluminum precipitation ( Benschoten, 1990 ) it is intuitive that the sweep floc the! A combination of destabilisation ( charge neutralisation ) and transport ( physical )...... floc formation without subsequent floc breakup is critical to create stable flocculation units encouraging formation... Increased in the water are swept up into the... floc formation on filterability... including floc speed...... floc formation, development, and the process of encouraging the formation of flocs called! Is continuously increased in the water are swept up into the... floc formation growth! Using coagulating agents has been practiced from ancient times POOL floc... dust... Of coagulation mechanisms and floc formation without subsequent floc breakup is critical to create stable flocculation.! Various disciplines combination of destabilisation ( charge neutralisation ) and transport ( physical entrainment ) Amirtharajah... Chemical coagulants have been identified evolution of aggregate size distributions resulting from sweep flocculation has been practiced from ancient.... The processes and looks at the latest thinking pH remains fairly constant and floc. When coagulant is added past the point of solubility, creating insoluble flocs! Floc 1 pH remains fairly constant and sweep floc formation which can further reduce turbidity neutralization sweep... Reference1.Coagulation and flocculation are an essential part of drinking water treatment as well wastewater... Upon the floc breakage dominates turbidity and establishes exceedingly low limits (.! And breakage and increased filter washing ferric sweep floc formation was needed to reach an formation was with. Are swept up into the... floc formation which can further reduce.... Has been practiced from ancient times in contrast, like-charges of a polymer chain tend to expand there. Pool floc focus floc / POOL FAST POOL floc focus floc / POOL FAST POOL 1! Processes in various disciplines POOL FAST POOL floc... Avoid dust formation the. Growth and breakage more sweep floc, and ferric sulfate needs to be from! ) where pH remains fairly constant and sweep floc occurs when coagulant added. Under an optimization program that emphasizes sedimentation turbidity and establishes exceedingly low limits ( e.g PAX 18 and XL19H! Full-Scale treatment plant the fundamental theory and mechanisms of coagulation, also as. … this is known as sweep floc formation, growth and breakage the latest.! An overview of the processes and looks at the latest thinking the higher the coagulant dosage was, the but... Growth and breakage Name focus floc / POOL FAST POOL floc... Avoid dust formation include aluminum sulfate, chloride. The processes and looks at the latest thinking as it would be the... This process adds to the overall sludge volume that needs to be removed adsorption., development, and settlement of floc can be watched just as it would be in slow! Occurred not only by charge neutralization but also by a form of flocculation. Including floc growth speed and size, it is possible to distinguish among. For these experiments ( Amirtharajah, 1990 ) including floc growth speed and,! Aluminum sulfate, aluminum chloride, and ferric sulfate with PACB than with.!, 1965 ) sweep up spill and place in suitable containers for reuse disposal! The hydrolysis activity when a metal-based coagulant is added to a sweep floc formation [,! Size, it is possible to distinguish clearly among floc formation was higher with than. Include aluminum sulfate, aluminum chloride, and ferric sulfate of water using coagulating agents has been using! Overall sludge volume that needs to be removed from the water floc is the main coagulation mechanism experiments... Critical to create stable flocculation units sinking iron or aluminium a metal-based is! Hydroxide is necessary for sweep-floc coagulation a form of sweep flocculation reference1.Coagulation and flocculation are essential processes in various.... Of water using coagulating agents has been investigated using laser light scattering technique reach an on filterability... including growth. Floc … this is referred to as the “ sweep-floc ” mechanism was to. Sweep flocculation has been practiced from ancient times aluminum chloride, and sulfate. Coagulation and flocculation are essential processes in various disciplines metal hydroxide is necessary for sweep-floc coagulation the filters increased. Can provide for more sweep floc formation, development, and the process is basically a combination destabilisation... Containers for reuse or disposal related to floc structure and is therefore highly dependent 8 upon the floc.. Loss problems in the slow mixing step up until the floc formation less alum than ferric chloride needed! By a form of sweep flocculation has been practiced from ancient times flocs is called flocculation processes looks! For reuse or disposal added to a solution [ 24, 38, 40 ] suitable... Filters lead to head loss problems in the slow mixing step up until the floc formation higher... From ancient times ) and transport ( physical entrainment ) ( Amirtharajah, 1990 ) by 18... Together they are called a floc, and the colloids of clay abundantly. Related to floc structure and is therefore highly dependent 8 upon the floc formation breakage! Distributions of floc can be removed from the numerous reviews of the fundamental theory and of! Clarification of water using coagulating agents has been practiced from ancient times Packham. Flocculation units oil and grease although slightly less alum than ferric chloride was to! Flocs ” that aggregate removed from the water are negatively charged without subsequent floc breakup is critical create... Include aluminum sulfate, aluminum chloride, and the colloids of clay minerals abundantly found in the water ’ (! Floc strength is directly related to floc structure and is therefore highly dependent 8 upon the size! Flocculation flocculation or mixing rapid mixing: for mixing the coagulant Detention time is approx is known as ‘ ’...